It is well known in prior art that the club orientation and acceleration up to golf ball impact, are critical parameters in determining an effective and repeatable stroke for any shot in golf. This is also known to be most problematic in putting, where the stroke pendulum is varied in response to the required putting distance, state of the greens, topography and the possible grain of the putting surface. A golfer assesses the conditions and required ball length to be traversed, and alters the length and perhaps speed of the putting stroke.
Deceleration during the downswing prior to contact with the ball is a particularly problematic condition known as the yips and is associated with an erratic stroke. More specifically, it is known that (1) Accelerating too quickly on the backstroke, during the transition stroke between the backstroke and the forward stroke, or during the forward stroke; and (2) Decelerating during the transition stroke or during the forward stroke are to be avoided.
At the time of ball contact, the club face should be perpendicular to the path of the putter head and the club face should strike the ball such that the club center of mass (or sweet spot) is aligned with the center of the ball.
In contrast to putting strokes, iron and wood shots are full shots, where a complete swing is used, and ball carry is primarily determined by the loft of the club and the momentum imparted to the ball from the club impact. In this case, the timing of the pendulum back-swing and downswing in relation to weight-shift are important in determining a repeatable stroke, but the length of the backswing and carry through should remain constant. In order to have a long carry with greater accuracy, the golf ball should be struck within a zone known as the sweet spot of the club and the swing should be such that the club face is aligned perpendicular to the golf ball at time of impact. Since both the arms and the wrists rotate during the downswing it takes precise timing of the swing to achieve club head alignment at impact. In such swings, the face of the club also can move at 30 m/s, making the observation and correction of the swing orbit and head position impossible to achieve by eye.
There are a number of golf swing practice devices which attempt to determine the face angle of a golf club head at the time of ball impact. For example, U.S. Pat. No. 4,615,526 uses a special club and magnetic sensors to measure club head velocity, and calculate face angle and ball carry using at least two or three discrete point sensors to sample the trajectory of the club. The relative timing between the sensor outputs are used together with dimensional knowledge of the distance between points to calculate swing parameters. U.S. Pat. No. 5,474,298 and U.S. Pat. No. 5,935,014 describe a golf swing apparatus that uses a number of coil loops in a planar detector mounted below the ball position and one or two magnets mounted in a spaced recess within the club. U.S. Pat. No. 5,435,561 describes a modified club that contains an inertial sensor device. These approaches have a severe shortcoming in that the sensors and technique requires the use of a special golf club or a golf club with special attachments, thus preventing the golfer from using his or her own clubs.
An alternate approach is to use optical sensors as described in U.S. Pat. No. 4,306,703, U.S. Pat. No. 5,614,823, U.S. Pat. No. 5,718,639, U.S. Pat. No. 5,976,022 and U.S. Pat. No. 6,375,579 B1. These and similar techniques are generally complex in construction and therefore expensive to manufacture or they utilize methods for detecting face angle which are not sufficiently accurate.
There are also a number of putting stroke training devices, for example U.S. Pat. Nos. 5,441,269 and 5,792,001 describe a putter club with orthogonal accelerometers that either contained within or mounted on the club and a system designed to train golfers. U.S. Pat. No. 5,435,561 describes the use of inertial sensors and an audio alarm to prevent rotation during a putt. A visual impact teaching system is described in U.S. Pat. No. 6,248,021 B1 uses an LED display matrix and pressure sensor on the face of the putter to display the ball impact point after a stroke. U.S. Pat. No. 4,180,270 describes a system for simulating a putting stroke using mechanically retractable pivot switch sensors, measuring the timing of these switches and relating them to swing training or the simulation of the path of an imaginary ball from a stroke. Some of the examples in the prior art describe methods determining where the ball strikes a putter, the alignment of the putter, aspects of the trajectory of the putter and feedback to the user. However, they are also either too complex in construction, or require the use of a special golf putter or putter with special attachments, thus preventing the golfer from readily using his or her own putter.
Golf simulators have become an important part of golf training and recreation. Various computer systems have been developed with advanced graphics to create a virtual golf environment. The most realistic systems make use of an actual golf ball, which is hit using conventional golf clubs in a netted booth. The trajectory of the ball is calculated using sensor technology which usually comprises complex optical, camera or radar systems. Radar systems have a particular shortcoming in that they are not able to accurately determine the ball trajectory. In addition, it is well known that putting makes up about 50% of the shots played in a typical round of golf. A method for accurately representing the trajectory of a putt and club head orientation is thus required for an enhanced golf simulator.
The principal object of the present invention and its embodiments is to provide a club head and/or ball displacement measurement apparatus that requires no attachments onto or modifications to the user golf club. The invention can be implemented as a golf training apparatus or as a sensor component for a golf simulator. A further object of the invention is to develop sensor technology that can be used with a users own set of clubs, that is suitable for measuring the state of the club head continuously over a zone just prior to and after ball impact, a means for transforming the path of the club head into a set of parameters to be used in training the user and a sensor technology that can utilized on both putting, iron and (driver) woods clubs.
The foregoing patents reflect the current state of the art of which the present inventor is aware. Reference to, and discussion of, these patents is intended to aid in discharging Applicant's acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the above-indicated patents disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein.